Suggestions on limiting SNMP and DHCP

We have mix of PMP 100, 450, and ePMP without NAT.  ePMP has security to limit DHCP request by limiting number of MAC connections on ethernet but I see no way of limiting SNMP to single IP -unless adding the IP of the trap server limits the SM to only the address.  The 450 gear has a way to limit SNMP to single IP (I think) but I see no way to limit DHCP request to number of desired MAC addresses.  I'd prefer to have this set at the SM and not in incase I should ever need to do a custom link.  Any advice?